Accelerate parsing by not re-checking previous data

While waiting for a <CR> the code would search through prevois received
characters, too. Keep track of what we've already checked to speed this
up.

diff --git a/module/can327.c b/module/can327.c
index aba198651476e1fe79f30ecdf4398e773e0d2c8d..833171cae03ceb55f5397be962cf9979b5dd9f6c 100644 (file)
--- a/module/can327.c
+++ b/module/can327.c
@@ -682,10 +682,9 @@ static void elm327_drop_bytes(struct can327 *elm, size_t i)
        elm->rxfill -= i;
 }
 
-static void elm327_parse_rxbuf(struct can327 *elm)
+static void elm327_parse_rxbuf(struct can327 *elm, size_t first_new_char_idx)
 {
-       size_t len;
-       int i;
+       size_t len, pos;
 
        lockdep_assert_held(&elm->lock);
 
@@ -696,20 +695,20 @@ static void elm327_parse_rxbuf(struct can327 *elm)
 
        case ELM327_STATE_GETDUMMYCHAR:
                /* Wait for 'y' or '>' */
-               for (i = 0; i < elm->rxfill; i++) {
-                       if (elm->rxbuf[i] == ELM327_DUMMY_CHAR) {
+               for (pos = 0; pos < elm->rxfill; pos++) {
+                       if (elm->rxbuf[pos] == ELM327_DUMMY_CHAR) {
                                elm327_send(elm, "\r", 1);
                                elm->state = ELM327_STATE_GETPROMPT;
-                               i++;
+                               pos++;
                                break;
-                       } else if (elm327_is_ready_char(elm->rxbuf[i])) {
+                       } else if (elm327_is_ready_char(elm->rxbuf[pos])) {
                                elm327_send(elm, ELM327_DUMMY_STRING, 1);
-                               i++;
+                               pos++;
                                break;
                        }
                }
 
-               elm327_drop_bytes(elm, i);
+               elm327_drop_bytes(elm, pos);
                break;
 
        case ELM327_STATE_GETPROMPT:
@@ -722,7 +721,7 @@ static void elm327_parse_rxbuf(struct can327 *elm)
 
        case ELM327_STATE_RECEIVING:
                /* Find <CR> delimiting feedback lines. */
-               len = 0;
+               len = first_new_char_idx;
                while (len < elm->rxfill && elm->rxbuf[len] != '\r')
                        len++;
 
@@ -756,7 +755,7 @@ static void elm327_parse_rxbuf(struct can327 *elm)
 
                        /* More data to parse? */
                        if (elm->rxfill)
-                               elm327_parse_rxbuf(elm);
+                               elm327_parse_rxbuf(elm, 0);
                }
        }
 }
@@ -935,12 +934,18 @@ static void can327_ldisc_rx(struct tty_struct *tty,
 #endif
 {
        struct can327 *elm = (struct can327 *)tty->disc_data;
+       size_t first_new_char_idx;
 
        if (elm->uart_side_failure)
                return;
 
        spin_lock_bh(&elm->lock);
 
+       /* Store old rxfill, so elm327_parse_rxbuf() will have
+        * the option of skipping already checked characters.
+        */
+       first_new_char_idx = elm->rxfill;
+
        while (count-- && elm->rxfill < ELM327_SIZE_RXBUF) {
                if (fp && *fp++) {
                        netdev_err(elm->dev, "Error in received character stream. Check your wiring.");
@@ -985,7 +990,7 @@ static void can327_ldisc_rx(struct tty_struct *tty,
                return;
        }
 
-       elm327_parse_rxbuf(elm);
+       elm327_parse_rxbuf(elm, first_new_char_idx);
        spin_unlock_bh(&elm->lock);
 }